合成4种成功能化酸性离子液体,采用红外光谱、热重分析等分析法进行表征验证,并用其催化菜籽油酯交换制备生物柴油,考察醇/油物质的量之比、反应温度、反应时间、离子液体用量和水含量对转化率的影响。结果表明,4种离子液体都有较强酸性,与浓硫酸酸性相当;带—SO3H基团的离子液体表现出更好的催化活性,且随着烷基链的增加,催化活性提高;在（n甲醇）∶n（菜籽油）=12∶1,反应温度130 ℃,反应时间3 h,离子液体（[BSO3HMIM][HSO4]）用量为菜籽油质量2%（质量分数）条件下,生物柴油转化率可达99%以上。在反应体系中,水会破坏离子液体的结构并导致其失活,而升高反应温度,可缓解水对离子液体的结构破坏,在130 ℃条件下,即使水分含量为5%时,生物柴油转化率仍可保持在约85%。
Abstract
In this study, four kinds of Brønsted acid ionic liquids （[PrMIM][HSO4]） , （[PrSO3HMIM][HSO4]）, （[BMIM][HSO4]）and （[BSO3HMIM][HSO4]） were synthesized by two-step method. Their structures were characterized by FTIR and TGA. And then, Brønsted acid ionic liquids were used as solid base catalyst to catalyze oil conversion and synthesis of biodiesel, the effects of molar ratio, reaction temperature, reaction time, catalyst amount and the deactivation of water on catalytic activity were investigated. The detection and analysis showed that their structures are in accordance with their theoretical structure. Their decomposition temperatures were higher than 200 ℃, so they were enough stable as the catalyst in synthesis of biodiesel. Brønsted acid ionic liquid with long alkyl chains and sulfonated groups exhibited the best catalytic activities due to their strong Brønsted acidity. Under the conditions of molar ratio of methanol to oil at 12∶1, mass fraction of ionic liquid（[BSO3HMIM][HSO4]） 2%（w）, reaction temperature 130 ℃ and reaction time 3 h, the conversion rate of biodiesel can reach more than 99%. Water molecules competed with the anion to bind with the protons of the imidazolium cation, which will destroy the structure of the ionic liquid and lead to inactivation. While increasing the reaction temperature could alleviate this negative effect of water. The conversion rate of biodiesel remained constant 85% at 130 ℃, even when the water content reaches 5%（w）.
关键词
生物柴油 /
离子液体 /
酯交换 /
磺化
Key words
biodiesel /
ionic liquid /
transesterification /
sulfonate
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基金
广东省科技计划（201804010125）; 国家重点研发计划（2017YFD0601003）; 国家自然科学基金（21576260）
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